Backlight module and liquid crystal display

ABSTRACT

Disclosed is a backlight module having light sources and a light guide plate, and the light guide plate has an incident side, and the lights emitted by the light sources pass through the incident side and enter into the light guide plate, and the a light direction changing layer is positioned at the incident side, and the light direction changing layer is employed for changing progress directions of the lights entering the incident side to shorten a distance perpendicular to the incident side from an intersection point of the lights emitted by adjacent light sources to the light sources. The present invention also discloses a liquid crystal display.

CROSS REFERENCE TO RELATED APPLICATION

This is a continuation of a U.S. patent application Ser. No. 13/380,894,filed on Dec. 26, 2011.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to a liquid crystal displayfield, and more particularly to a backlight module and a liquid crystaldisplay.

2. Description of Prior Art

With the population of the liquid crystal display, the demands for thedisplay function of the liquid crystal display are getting higher andhigher.

FIGS. 1A and 1B depict partial structure diagrams of a backlight moduleaccording to a prior art. Please refer to FIG. 1A. FIG. 1A shows asectional diagram of the backlight module. As designing the lightEmitting Diodes (LEDs) 11 and the light guide plate 12, the couplingefficiency of the lights emitted by the LEDs 11 including the couplingefficiency of the lights progressing from the LEDs 11 to the light guideplate (LGP) 12 has to be considered. Please refer to FIG. 1B. FIG. 1B isa sectional diagram of FIG. 1A. When the distance between the LEDs 11and the light guide plate 12 is S1, all the lights emitted by the LEDs11 can enter into the light guide plate 12.

Similarly, the distance perpendicular to the light guide plate 12 fromthe intersection point of the lights emitted by the adjacent LEDs 11 tothe LEDs 11 also needs to be considered. For example, the lights emittedby the LEDs 11 enter the light guide plate 12 are illustrated in FIG.1A. After the light emitted by one LED 11 enters into the light guideplate 12 and progresses a light coupling distance D1 in the direction B1perpendicular to the incident side of the light guide plate 12, thelight intersects with the light emitted by the adjacent LED 11.Therefore, the lights are emitted by the adjacent LEDs 11 and intersect,a dark area 13 is formed thereby and no light exist in the dark area 13.

Generally, the material of the light guide plate 12 is PMMA(Polymethylmethacrylate). Because the refractive index of the PMMA islarger than the refractive index of the air, the lights will berefracted toward the normal line L after the light emitted by the LED 11progresses into the light guide plate 12 from the air. That is, theincidence angle θ1 is larger than the departure angle θ2 and thedistance D1 (the light coupling distance) in the direction B1perpendicular to the light guide plate 12 from the intersection point ofthe lights emitted by the adjacent LEDs 11 to the LEDs 11 becomeslarger. Once the light coupling distance D1 becomes large enough to makethe dark areas 13 occur in display area 14. The phenomenon of bright anddark mixing display can be happen on the liquid crystal panel.

For shortening the light coupling distance D1 to prevent the occurrenceof dark areas 13 in the display area 14, a feasible method is toincrease the distance between the LEDs 11 and the light guide plate 12.Please refer to FIG. 2A, the distance between the LEDs 11 and the lightguide plate 12 is enlarged as S2 and S2>S1. Although the progressingpath of the lights in the direction B1 perpendicular to the light guideplate 12 is longer to decrease the light coupling distance as D2 andD2<D1 to prevent the occurrence of dark areas 13 in the display area 14.However, please refer to FIG. 2B, which is a sectional diagram of FIG.2A, not all the lights emitted by the LEDs 11 can enter the light guideplate 12. Accordingly, the coupling efficiency of the lights in thedirection B1 perpendicular to the light guide plate 12 becomesdescended.

In conclusion, it is a research and development aspect of the liquidcrystal manufacture skill related with how to shorten a distanceperpendicular to the light guide plate from an intersection point of thelights emitted by the adjacent LEDs to the LEDs and prevent theoccurrence of dark areas in the display area of the liquid crystal panelas the lights of the LEDs intersect for guaranteeing the display qualityof the liquid crystal panel.

SUMMARY OF THE INVENTION

An objective of the present invention embodiments is to provide abacklight module to shorten a distance perpendicular to the incidentside from an intersection point of the lights emitted by the adjacentLEDs to the LEDs to prevent the occurrence of dark areas in the displayarea of the liquid crystal panel as the lights of the LEDs intersect andto guarantee the display quality of the liquid crystal panel.

For achieving the aforesaid beneficial effect, the present inventionconstructs a backlight module having light sources and a light guideplate, and the light guide plate has an incident side with a firstrefractive index, and the lights emitted by the light sources passthrough a medium and the incident side and enter into the light guideplate, and the medium has a third refractive index;

a distance between the light source and a light direction changing layeris a light coulping distance, and the light coulping distance is apredetermined distance for all the lights emitted by the light sourcesto enter into the light direction changing layer;

the light direction changing layer is positioned at the incident side,and the light direction changing layer has a second refractive index,and the second refractive index is smaller than the first refractiveindex and larger than the third refractive index; the light directionchanging layer is employed for changing progress directions of thelights entering the incident side to shorten a distance perpendicular tothe incident side from an intersection point of the lights emitted byadjacent light sources to the light sources.

In the backlight module of the present invention, the light directionchanging layer is a transparent film, and material of the transparentfilm is silicon dioxide or calcium fluoride.

In the backlight module of the present invention, the transparent filmis coated on the incident side of the light guide plate.

Another objective of the present invention is to provide a backlightmodule to shorten a distance perpendicular to the incident side from anintersection point of adjacent LEDs to the LEDs to prevent theoccurrence of dark areas in the display area of the liquid crystal panelas the lights of the LEDs intersect and to guarantee the display qualityof the liquid crystal panel.

For attaining the aforesaid beneficial effect, the present inventionconstructs having light sources and a light guide plate, and the lightguide plate has an incident side, and the lights emitted by the lightsources pass through the incident side and enter into the light guideplate;

a light direction changing layer is positioned at the incident side, andthe light direction changing layer is employed for changing progressdirections of the lights entering the incident side to shorten adistance perpendicular to the incident side from an intersection pointof the lights emitted by adjacent light sources to the light sources.

In the backlight module of the present invention, a distance between thelight source and a light direction changing layer is a light coulpingdistance, and the light coulping distance is a predetermined distancefor all the lights emitted by the light sources to enter into the lightdirection changing layer.

In the backlight module of the present invention, the light guide platehas a first refractive index, and the lights emitted by the lightsources pass through a medium and enter into the light guide plate, andthe medium has a third refractive index; the light direction changinglayer has a second refractive index, and the second refractive index issmaller than the first refractive index and larger than the thirdrefractive index.

In the backlight module of the present invention, the light directionchanging layer is a transparent film, and material of the transparentfilm is silicon dioxide or calcium fluoride.

In the backlight module of the present invention, the transparent filmis coated on the incident side of the light guide plate.

Another objective of the present invention is to provide a liquidcrystal display, and the liquid crystal display comprises a backlightmodule having light sources and a light guide plate, and the light guideplate has an incident side, and the lights emitted by the light sourcespass through the incident side and enter into the light guide plate;

a light direction changing layer is positioned at the incident side, andthe light direction changing layer is employed for changing progressdirections of the lights entering the incident side to shorten adistance perpendicular to the incident side from an intersection pointof the lights emitted by adjacent light sources to the light sources.

In the liquid crystal display of the present invention, a distancebetween the light source and a light direction changing layer is a lightcoulping distance, and the light coulping distance is a predetermineddistance for all the lights emitted by the light sources to enter intothe light direction changing layer.

In the liquid crystal display of the present invention, the light guideplate has a first refractive index, and the lights emitted by the lightsources pass through a medium and enter into the light guide plate, andthe medium has a third refractive index; the light direction changinglayer has a second refractive index, and the second refractive index issmaller than the first refractive index and larger than the thirdrefractive index.

In the liquid crystal display of the present invention, the lightdirection changing layer is a transparent film, and material of thetransparent film is silicon dioxide or calcium fluoride.

In the liquid crystal display of the present invention, the transparentfilm is coated on the incident side of the light guide plate.

Comparing with prior arts, the present invention positions a lightdirection changing layer at the incident side, and the refractive indexof the light direction changing layer is smaller than the refractiveindex of the light guide plate and a light coulping distance between thelight source and a light direction changing layer is a predetermineddistance. Accordingly, the lights emitted by the light sources enter thelight guide plate before they are refracted by the light directionchanging layer. Because the light coulping distance is the predetermineddistance, all the lights emitted by the light sources can enter into thelight guide plate. The coupling efficiency on the directionperpendicular to the light guide plate is well guaranteed; furthermore,a distance perpendicular to the incident side from an intersection pointof the lights emitted by adjacent light sources to the light sources isshortened. Therefore, the occurrence of the dark areas in the displayarea of the liquid crystal panel can be effectively prevented and thedisplay quality of the liquid crystal panel can be ensured.

For a better understanding of the aforementioned content of the presentinvention, preferable embodiments are illustrated in accordance with theattached figures for further explanation:

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B depict partial structure diagrams of a backlight moduleaccording to a prior art;

FIGS. 2A and 2B depict structure diagrams in which a distance betweenthe LEDs and the light guide plate shown in FIGS. 1A and 1B is changed;

FIG. 3 depicts a structure diagram of a preferable embodiment accordingto the present invention;

FIG. 4 depicts a sectional diagram of FIG. 3;

FIG. 5 depicts a diagram of the light progress directions shown in FIG.3.

DETAILED DESCRIPTION OF THE INVENTION

The following clear and full descriptions for the respective embodimentsare specific embodiments capable of being implemented for illustrationsof the present invention with referring to appended figures.

FIG. 3 depicts a structure diagram of a preferable embodiment accordingto the present invention. The backlight module has a light source 31 anda light guide plate 32. The light guide plate 32 has an incident side321. A light direction changing layer is positioned at the incident side321. The light direction changing layer is employed for changingprogress directions of the lights entering the incident side to shortena distance in a direction B1 perpendicular to the incident side 321 froman intersection point of the lights emitted by adjacent light sources 31to the light sources 31.

As mentioning “shortening distance” in this embodiment, it refers to adistance between the intersection point of the lights emitted by theadjacent light sources 31 and the light sources 31 in a direction B1perpendicular to the incident side 321. Comparing to the prior arts, thedistance can be shortened, such as two millimeters. Please refer thecontents hereafter for details.

As being a preferable embodiment, the light direction changing layer isa refracting layer 33. Certainly, the light direction changing layeralso can be a scattering layer if only the progress directions of thelights can be changed and the distance of the intersection point of thelights emitted by adjacent light sources 31 in a direction B1perpendicular to the incident side 321 can be shortened. Here, theenumerations therefor are omitted.

Preferably, the light sources 31 are LEDs. Certainly, the light sources31 can be other illuminants. The refracting layer 33 is a transparentfilm, and material of the transparent film is silicon dioxide or calciumfluoride.

In one specific embodiment, the refracting layer 33 is laminated to theincident side 321 of the light guide plate 32. More preferably, therefracting layer 33 as a transparent film can be coated on the incidentside 321 of the light guide plate 32. Certainly, other methods also canbe illustrated and the enumerations therefor are omitted here.

The light guide plate has a first refractive index n1. The medium has athird refractive index. The refracting layer 33 has a second refractiveindex n2. The lights emitted by the light sources 31 pass through amedium and enter into the light guide plate 32. The medium has a thirdrefractive index n3. The second refractive index n2 is smaller than thefirst refractive index n1 and larger than the third refractive index n3.

For instance, the medium is air and the refractive index is 1.0; thematerial of the light guide plate 32 is Polymethylmethacrylate and therefractive index of the light guide plate 32 is 1.49; as the material ofthe refracting layer 33 is silicon dioxide, the refractive index of therefracting layer 33 is 1.45. Certainly, the refracting layer 33 also canbe made by other materials if only the refractive index n2 of therefracting layer 33 is smaller than the refractive index n1 of the lightguide plate 32. Here, the enumerations therefor are omitted.

For instance, as the material of the refracting layer 33 is silicondioxide, the refractive index of the refracting layer 33 is 1.45; as thematerial of the refracting layer 33 is calcium fluoride, the refractiveindex of the refracting layer 33 is 1.33.

Please refer to FIG. 4. The distance between the light sources 31 andthe refracting layer 33 is a light coupling distance. The light couplingdistance is a predetermined distance. As the light coupling distance isthe distance indicated by S1 shown in FIG. 4, all the lights emitted bythe light sources 31 can enter the refracting layer 33 and the lightcoupling efficiency of the lights in the direction B1 perpendicular tothe incident side 32 can be guaranteed.

The functional principle of the backlight module according to thepreferable embodiment of the present invention is introduced hereafter:

Please refer to FIG. 3, FIG. 4 and FIG. 5. The lights emitted by thelight sources 31 pass through the medium and then arrive and enter intothe refracting layer 33. Because the second refractive index n2 of therefracting layer 33 is larger than the third refractive index n3 of themedium, the progress direction of the light is changed toward a firstnormal line L2 after the light progresses and enters into the refractinglayer 33. Namely, the first incidence angle θ3 of the light is largerthan the second incidence angle θ4 which the light enters into the lightguide plate with.

The light entering into the refracting layer 33 keeps progressing andenters the light guide plate 32. Because the second refractive index n2of the refracting layer 33 is smaller than the first refractive index n1of the light guide plate 32, the progress direction of the light ischanged toward a second normal line L3 after the light progresses andenters into the light guide plate 32. Therefore, the second incidenceangle θ4 which the light enters into the light guide plate 32 with islarger than the second departure angle θ5.

Apparently, comparing with the light directly entering the light guideplate 12 shown in FIG. 1, in this embodiment, the light passes throughthe refracting layer 33 which the refractive index is smaller than therefractive index of the light guide plate 12 for refracting the lightbefore entering the light guide plate 32 and a light coulping distanceS1 is maintained between the light source 31 and the refracting layer33. Therefore, the light enters into the light guide plate 32 afterbeing refracted by the refracting layer 33. The distance in thedirection B1 perpendicular to the incident side 321 from theintersection point of the lights emitted by the adjacent LEDs 31 to theLEDs 31 is apparently shortened as D3. The light coulping distance D3 inthis embodiment is smaller than the light coulping distance D1 shown inFIG. 1, i.e. D3<D1 and the difference is D1-D3. Accordingly, the presentinvention is capable of effectively preventing the occurrence of thedark area 34 in the display area 35 of the liquid crystal panel as thelights of the LEDs 31 intersect and still remains the light coulpingdistance as S1 for allowing all the lights emitted by the light sources31 entering the into the refracting layer 33. The coupling efficiency ofthe lights in the direction B1 perpendicular to the incident side 321can be ensured and the display quality of the liquid crystal panel canbe guaranteed.

Furthermore, in the embodiment, the distance in the direction B1perpendicular to the incident side 321 from the intersection point ofthe lights emitted by the adjacent light sources 31 to the light sources31 is shortened as D3, even the space D4 between adjacent light sources31 are wider, the occurrence of the dark area 34 in the display area 35of the liquid crystal panel as the lights of the light sources 31intersect still can be prevented. Accordingly, the present invention iscapable of decreasing the amount of the light sources 31 and save thecost.

Moreover, the distance in the direction B1 perpendicular to the incidentside 321 from the intersection point of the lights emitted by theadjacent light sources 31 to the light sources 31 is shortened as D3, incomparison with the display area 14 of the prior art, the area of thedisplay area 35 can be tremendously increased according to thisembodiment. That is, the occurrence of the dark area 34 in the displayarea 35 of the liquid crystal panel as the lights of the light sources31 intersect can be similarly prevented, even the thickness D5 requiredin the frame edge design of the light guide plate 32 for guaranteeingthe light coupling is diminished. Accordingly, the narrow frame designcan be realized and the occupied space of the liquid crystal panel canbe decreased for saving the cost.

The present invention also provides a liquid crystal display. The liquidcrystal display comprises the backlight module provided by the presentinvention as aforementioned with detail description. Here, repeat is nomore.

As is understood by a person skilled in the art, the foregoing preferredembodiments of the present invention are illustrative rather thanlimiting of the present invention. It is intended that they covervarious modifications and similar arrangements be included within thespirit and scope of the appended claims, the scope of which should beaccorded the broadest interpretation so as to encompass all suchmodifications and similar structure.

What is claimed is:
 1. A backlight module, comprising light sources anda light guide plate, the light guide plate having an incident side, andthe lights emitted by the light sources passing through the incidentside and entering into the light guide plate, characterized in that: adistance between the light source and a light direction changing layeris a light coulping distance, and the light coulping distance is apredetermined distance for all the lights emitted by the light sourcesto enter into the light direction changing layer; a light directionchanging layer is positioned at the incident side and is laminated tothe incident side of the light guide plate, the light direction changinglayer is coated on the incident side of the light guide plate and thelight direction changing layer is employed for changing progressdirections of the lights entering the incident side to shorten adistance perpendicular to the incident side from an intersection pointof the lights emitted by adjacent light sources to the light sources;wherein a distance between the light sources and the light directionchanging layer is a light coupling distance, all the lights emitted bythe light sources can enter the light direction changing layer.
 2. Thebacklight module according to claim 1, characterized in that the lightguide plate has a first refractive index, and the lights emitted by thelight sources pass through a medium and enter into the light guideplate, and the medium has a third refractive index, characterized inthat: the light direction changing layer has a second refractive index,and the second refractive index is smaller than the first refractiveindex and larger than the third refractive index.
 3. A liquid crystaldisplay, characterized in that, the liquid crystal display comprises abacklight module having light sources and a light guide plate, and thelight guide plate has an incident side, and the lights emitted by thelight sources pass through the incident side and enter into the lightguide plate; a light direction changing layer is positioned at theincident side and is laminated to the incident side of the light guideplate, and the light direction changing layer is employed for changingprogress directions of the lights entering the incident side to shortena distance perpendicular to the incident side from an intersection pointof the lights emitted by adjacent light sources to the light sources;wherein the light guide plate has a first refractive index, and thelights emitted by the light sources pass through a medium and enter intothe light guide plate, and the medium has a third refractive index, thelight direction changing layer has a second refractive index, and thesecond refractive index is smaller than the first refractive index andlarger than the third refractive index.
 4. The liquid crystal displayaccording to claim 3, characterized in that a distance between the lightsource and the light direction changing layer is a light coulpingdistance, and the light coulping distance is a predetermined distancefor all the lights emitted by the light sources to enter into the lightdirection changing layer.
 5. The liquid crystal display according toclaim 4, characterized in that the light direction changing layer is atransparent film, and material of the transparent film is silicondioxide or calcium fluoride.
 6. The liquid crystal display according toone of claim 5, characterized in that the transparent film is coated onthe incident side of the light guide plate.